Deodorant compositions

ABSTRACT

A deodorant composition for topical application, which comprises a plurality of particles dispersed and a carrier, each particle comprising a glass microsphere at least partially coated with zinc oxide, a zinc salt, or any mixture of two or more thereof.

BACKGROUND

[0001] This invention relates to deodorant compositions.

[0002] Zinc oxide is known to have bactericidal properties, and has beenwidely used in deodorant compositions. It is believed to work by thezinc ions of the zinc oxide going into solution in the outer layer ofthe skin, where they kill microorganisms by preventing enzymes thereinfrom functioning properly.

[0003] Inhalation of zinc oxide particles smaller than about 10micrometers can cause adverse reactions in humans and animals. For thisreason, many countries have adopted Health and Safety legislationforbidding the use of zinc oxide particles smaller than 10 micrometersin aerosols. This places a lower limit on the size of zinc oxideparticles that can be used in aerosol deodorant compositions.

[0004] Although zinc oxide particles can easily be made to a sizegreater than 10 micrometers, such particles appear as a white powder andare considered unsightly. In order to avoid this white appearance itwould be necessary to use a zinc oxide particle size below 10micrometers, but this would not be permitted under the legislationreferred to above.

[0005] Spherical particles comprising a zinc oxide coating are known.Thus, U.S. Pat. No. 5,407,743 describes electromechanical devices suchas transducers which comprise glass spheres of size 1 to 500 micronscoated with zinc oxide. The zinc oxide coating is formed by applying azinc oxide precursor to the spheres and then contacting the coatedspheres with an oxidizing agent to form a zinc oxide coating on thespheres.

[0006] J. Soc. Cosmet. Chem., 41, 197-207 (May/June 1990) describes amechanochemical process wherein fine particle zinc oxide is mixed withspherical resin cores to provide a hybrid powder of cores with theirsurfaces uniformly covered with zinc oxide. The powder has deodorizingqualities.

SUMMARY OF THE INVENTION

[0007] We have now devised some deodorant compositions containing zincoxide, or a zinc salt, whereby one or more of a number of advantagesover prior known compositions can be obtained including, if desired, theadvantage of substantially transparent zinc oxide (or zinc salt) withoutthe need to use particles having a size below 10 micrometers.

[0008] According to one aspect of the invention, we provide a deodorantcomposition for topical application, which comprises a plurality ofparticles which each comprise a glass microsphere at least partiallycoated with a zinc compound sintered to the glass microsphere, the zinccompound being selected from zinc oxide, a zinc salt or any mixture oftwo or more thereof, said particles being dispersed in a carrier.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a graph of log [colony forming units per cm²] versustime for coryneform bacteria; and

[0010]FIG. 2 is a graph of log [colony forming units per cm²] versustime for staphylococci bacteria.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] In the compositions of the present invention, the microspheresmay be coated only with zinc oxide, or with both zinc oxide and a zincsalt, or with a salt alone (mixtures of two or more salts can be used).We prefer that the coating comprises zinc oxide and a salt since thenthe bactericidal activity of the zinc oxide is enhanced and the productremains active for an extended period. If the coating consists only ofone or more zinc salts with no zinc oxide present, the activebactericidal life of the coating is usually relatively short. If thecoating consists of zinc oxide alone, its bactericidal activity is notas great as when a zinc salt is also present.

[0012] The preferred zinc salts are those which can be made by reactinga zinc oxide coating with an acid to form the salt in situ on themicrospheres. Preferably, the zinc salts are only sparingly soluble inwater so that they are not quickly removed by contact with water. Thepreferred salts are made by reacting the zinc oxide with a carboxylicacid or a substituted phenol. Examples of the preferred salts are theacetate, pidolate, pyrrolidone-5-carboxylate, cinnamate, citrate andglycinate, but these are merely illustrative of the many possible saltswhich can advantageously be used.

[0013] The compositions according to the invention may also contain atleast one further bactericide in addition to the zinc oxide or zincsalt.

[0014] The colour of the particles depends upon the colour of the glassmicrosphere core, because the layer of the zinc compound (by which wemean zinc oxide and/or one or more zinc salts) will be substantiallytransparent, provided that it is thin enough. This makes it possible toprovide a deodorant composition which has the bactericidal advantages ofzinc oxide without the white appearance normally associated withdeodorant compositions containing zinc oxide particles larger than 10microns. In order to comply with legislation relating to the size ofzinc oxide particles in aerosols, the glass microspheres would normallyhave a minimum diameter of about 10 micrometers, although for otheruses, they may of course be smaller, eg. down to 5 micrometers or less.We have found that, in order to obtain good transparency, it ispreferable that the diameter of the glass microspheres should not exceedabout 50 micrometers. However, greater diameters can be used, forexample up to 150 micrometers or more.

[0015] In order to prepare the zinc oxide coated microspheres of theinvention, it is important to control the reaction temperature closely.In accordance with another aspect of the invention, we provide a methodof coating glass microspheres with zinc oxide, which method comprisesheating an agitated mixture of the glass microspheres and a zinccompound in a liquid reaction medium to form a milky suspension ofcolloidal zinc oxide, and further heating the suspension to 190° C. to200° C. to deposit the zinc oxide as an adherent coating sintered on theglass microspheres. We have found that if the temperature is outsidethis range, then either the yield of zinc oxide or the adherence of thecoating, or both, will be generally unsatisfactory.

[0016] We have also found that heating in two stages, at two differenttemperatures, provides the best combination of adhesion and yield.Accordingly, we prefer to form the milky suspension by heating themixture to 140° C. to 160° C., preferably for 1 to 3 hours. Then, weprefer to heat for a further 1 to 3 hours to deposit said coating at190° to 200° C.

[0017] The method of the invention is carried out in a liquid reactionmedium. This should have a high enough dielectric constant that itdissolves the zinc compound, and also a high enough boiling point toallow the high temperatures to be obtained to produce the zinc oxide andallow sintering of the coating on the surface of the glass microspheres.Among the preferred such solvents are the glycols, particularly (but notexclusively) diethylene glycol, tetraethylene glycol and poly(ethyleneglycol). Diethylene glycol has a dielectric constant of 31.7 at 20° C.and a boiling point of 245° C. Poly(ethylene glycol) of molecular weight300 has a dielectric constant of 37.7 at 20° C. and a boiling point of198° C.

[0018] Any zinc compound can be used which will hydrolyse in the processto yield zinc oxide. The preferred zinc compounds are the carboxylates(other than the oxalate), most preferably the acetate. The chloride andsulphate are not used since zinc oxide is not readily formed therefromin glycol solutions. As will be clear to those skilled in the art, thesuitability of any particular zinc compound can be ascertained byroutine trial and experiment.

[0019] When the zinc compound used is zinc acetate dihydrate, we preferthe glycol to be diethylene glycol, tetraethylene glycol orpoly(ethylene glycol) of molecular weight 300 (PEG Mr 300). The use ofthese glycols leads to the formation of the zinc oxide as a single phasewhich is preferred. Other glycols can also be used although some maylead to the formation of the less desirable impure multiphase compounds.In general, any glycol can be used but we prefer to use one of the abovethree or any mixture of two or all three thereof.

[0020] According to a further feature of the invention, when it isdesired that the coating on the microspheres should comprise a zincsalt, the salt can be formed in situ by reacting the zinc oxide coatingwith an acid. We prefer to form a layer of a zinc salt at the exposedsurface of the zinc oxide, so that the product comprises microsphereswith a zinc oxide coating having zinc salt thereon. However, if desired,the whole of the zinc oxide can be reacted with acid so that the productthen comprises microspheres with zinc salt coatings (and no zinc oxide).

[0021] The zinc oxide coating of the invention comprises submicronprimary particles or crystallites of the zinc oxide with diameters inthe region of, for example, about 30 nm. These colloidal particlesaggregate and form particulate clusters with diameters in the range ofabout 0.3 to about 0.5 micrometers. The size of the primary particlescan be controlled by varying the reaction temperature as described morefully hereinafter.

[0022] It is usually preferred for the compositions of the invention tobe transparent, in which case the glass microspheres are preferablysubstantially transparent. However, there may be circumstances in whichit is desirable for the composition to have a particular colour. It ispossible to provide the composition with a desired colour by using glassmicrospheres having the desired colour.

[0023] The compositions according to the invention may be provided inany convenient form suitable for topical application. For example, thecompositions may be provided in the form of an aerosol, roll-on, gel,stick, cream, lotion or pump spray formulation.

[0024] In the compositions of the invention, the carrier is preferably adermatologically acceptable vehicle such as, for example, a polyhydricalcohol, a silicone, ethanol, water etc. or any mixture of two or morethereof.

[0025] The compositions of the invention may be formulated into topicalcompositions such as aerosols, pump sprays, roll-ons, lotions, creams,gels, sticks etc. In particular, aqueous suspensions of the zinc oxideparticles and salts may be directly utilized in oil-in-water andwater-in-oil emulsions, such as the currently popular clear gelformulations, or in other aqueous based compositions such as aqueousbased roll-ons. The compositions of the invention may be formulated intoany known type of topical composition which utilizes powdered saltsincluding, in particular, aerosol, liquid roll-on, cream and solid stickformulations in which the powdered salt is suspended in an anhydrous,dermatologically acceptable carrier, particularly a carrier comprising asilicone.

[0026] It will be appreciated that the precise formulation of thedeodorant compositions will depend upon the type of deodorantcomposition which is desired. Thus, an aerosol formulation will containpredominantly a propellant, such as CAP30 propellant; a stick typeformulation will typically contain predominantly propylene glycol; aroll-on formulation will typically contain predominantly cyclomethicone;and a gel formulation will typically contain predominantly water andpropylene glycol. The deodorant compositions according to the inventionmay include any of the materials conventionally used in deodorantformulations. The compositions of the invention may comprise, inaddition to the zinc oxide coated particles, other different particles.

[0027] The deodorant compositions according to the invention willcontain sufficient zinc compound coated microspheres to reduce orprevent malodour when applied to the skin. Typically, they will containfrom 0.1 to 25 wt % of the zinc compound coated microspheres. It ispreferred that the compositions comprise 5 to 15 wt % of the zinccompound coated microspheres, more preferably up to about 10 wt %.

[0028] In accordance with another aspect of the invention, we provide anaerosol, roll-on, gel or pump spray device which includes a deodorantcomposition as described above.

[0029] According to another aspect of the invention we provide the useof particles comprising glass microspheres coated with a zinc compoundas a deodorant in compositions for topical application. The particlesmay have the features of the particles of the deodorant compositiondescribed above.

[0030] The invention will now be described with reference to thefollowing Examples.

EXAMPLE 1

[0031] Zinc acetate dihydrate (44 g) and sodalime glass microspheres (22g) were added to a 1 liter reaction kettle containing 500 ml ofdiethylene glycol. The sodalime glass microspheres were obtained fromCroxton & Gary under the trade name Spheriglass 2000 cpo, and had adiameter in the range 10 to 50 micrometers.

[0032] A flanged lid with a propeller type stirring paddle was placedover the reaction kettle. The kettle was then placed in an oil bath andsubjected to a heating cycle of 2 hours at 150° C. followed by 2 hoursat 190° C. On completion of the heating, the kettle was removed from theoil bath and the diethylene glycol was decanted off. The remaining zincoxide coated glass microspheres were filtered and washed in ethanol. Thecoated microspheres were then dried at room temperature.

[0033] A sample of the microspheres was coated with gold, then subjectedto SEM analysis. This showed that the zinc oxide is present as clustersof primary particles.

[0034] These zinc oxide clusters consist of aggregates of much smallerzinc oxide primary particles. The primary particles are nm sized, andthey are aggregated together to form the larger sub-micron sized (eg.0.3-0.5 μm) clusters.

[0035] The zinc oxide coated microspheres prepared by this method can beused to form a variety of deodorant compositions, as exemplified inExamples 2 to 5.

EXAMPLE 2

[0036] An aerosol type deodorant was prepared from the followingmaterials: CAP30 propellant   80 wt % ZnO coated microspheres  2.5 wt %Ethanol 11.5 wt % Volatile silicone DC245   6 wt %

EXAMPLE 3

[0037] A stick type deodorant was prepared from the following materials:Water 12 wt % Propylene glycol 71 wt % Sodium stearate  8 wt % ZnOcoated microspheres  8 wt % Perfume  1 wt %

EXAMPLE 4

[0038] A suspension roll-on type deodorant was prepared from thefollowing materials: Cyclomethicone  86 wt % ZnO coated microspheres   8wt % Ethanol 2.5 wt % Quaternium 18 Hectorite   2 wt % Perfume 1.5 wt %

EXAMPLE 5

[0039] A gel type deodorant was prepared from the following materials:Water 25.25 wt % Sorbitol   14 wt % Ethanol   12 wt % Propylene glycol 22.5 wt % ZnO coated microspheres    8 wt % Dimethicone (DC-225)   10wt % Cyclomethicone & dimethicone    8 wt % copolyol Perfume  0.25 wt %

EXAMPLE 6

[0040] A modified zinc oxide coating was prepared by reacting the ZnOcoated microspheres with eugenol (4-allyl-2-methoxyphenol). Thefollowing formulation was prepared: Acetone 89 wt % Eugenol  5 wt % ZnOcoated microspheres  4 wt % Distilled water  2 wt %

[0041] The formulation was stirred at room temperature for 48 hours,then the modified ZnO coated microspheres were isolated by filtration,washed and dried at room temperature.

EXAMPLE 7

[0042] A modified zinc oxide coating was prepared by reacting the ZnOcoated microspheres with pyrrolidone-5-carboxylic acid. The followingformulation was prepared: Pyrrolidone-5-carboxylic acid  5 wt % ZnOcoated microspheres  4 wt % Distilled water 91 wt %

[0043] The formulation was stirred at room temperature for 48 hours,then the modified ZnO coated microspheres were isolated by filtration,washed and dried at room temperature.

EXAMPLE 8

[0044] An in-vivo method, known as the Williamson and Kligman surfacescrub, was used to demonstrate the antimicrobial properties of thefollowing five compositions:

[0045] (A) A control composition comprising ethanol/volatile silicone

[0046] (B) A composition comprising ethanol/volatile silicone and 0.3 wt% of a well known deodorant known as Triclosan(2,4,4′-trichloro-2-hydroxybiphenyl ether). This concentration is thehighest amount of Triclosan that can be used without skin irritation.

[0047] (C) A composition according to the invention comprising ethanol/volatile silicone containing 2.5 wt % of the zinc oxide coated particlesobtained by the method of Example 1.

[0048] (D) A composition according to the invention comprising ethanol/volatile silicone containing 10 wt % of the zinc oxide coated particlesobtained by the method of Example 1.

[0049] (E) A composition according to the invention comprising ethanol/volatile silicone containing 20 wt % of the zinc oxide coated particlesobtained by the method of Example 1.

[0050] In all the above compositions, the ratio of ethanol to siliconewas 70/30, and there were substantially no other components presentexcept those indicated.

[0051] The test was designed to measure the growth of the bacteriastaphylococci and coryneforms in the axilla of each member of a group ofparticipants. These two types of bacteria are primarily responsible forthe development of odours.

[0052] Initially, a sample of bacteria was removed from the axilla ofeach participant. A 0.5 ml aliquot of various deodorant compositions wasthen applied to the axilla of the participants, and further bacteriasamples were removed after 2, 7 and 24 hours. The level of coryneformsand staphylococci in each sample were then measured.

[0053] Bacteria level counts were obtained for each sample, and thechange in bacteria levels with time is shown in FIGS. 1 and 2. The blackdotted line represents the level of bacteria at which odours start tobecome detectable. It is clear that compositions (C), (D) and (E) aresubstantially more effective than compositions (A) or (B). The resultsshow that compositions (C), (D) and (E) were effective againstcoryneforms for up to 24 hours. Furthermore, the compositions (C), (D)and (E) did not cause any skin irritation.

1. A deodorant composition for topical application, which comprises aplurality of particles which each comprise a glass microsphere at leastpartially coated with a zinc compound sintered to the glass microsphere,the zinc compound being selected from the group consisting of zincoxide, a zinc salt and a mixture of at least two thereof, said particlesbeing dispersed in a carrier.
 2. A composition according to claim 1,wherein the coating comprises zinc oxide and a zinc salt.
 3. Acomposition according to claim 2, wherein the zinc salt is selected fromthe group consisting of zinc pidolate, zinc acetate, zinc eugolinate,zinc pyrrolidone-5-carboxylate, zinc cinnamate, zinc citrate and zincglycinate.
 4. A composition according to claim 1, wherein the zinc saltis formed by contacting a zinc oxide coating on the microspheres with anacid.
 5. A composition according to claim 4, wherein the acid isselected from the group consisting of a carboxylic acid and a phenol. 6.A composition according to claim 1, which also contains at least onefurther bactericide in addition to the zinc oxide.
 7. A compositionaccording to claim 1, wherein the glass microspheres have a diameter offrom 5 to 150 micrometers.
 8. A composition according to claim 7,wherein the glass microspheres have a diameter of from 10 to 50micrometers.
 9. A composition according to claim 1, wherein the zincoxide or zinc salt is present in the coating in particle clusters of adiameter from 0.3 to 0.5 micrometers.
 10. A composition according toclaim 8, wherein said particles are substantially transparent.
 11. Acomposition according to claim 1, wherein the carrier is adermatologically acceptable vehicle.
 12. A composition according toclaim 11, wherein the carrier is selected from the group consisting of apolyhydric alcohol, a silicone, ethanol, water and a combination of atleast two thereof.
 13. A composition according to claim 1, whichcontains from 0.1 to 25 wt. % of the particles.
 14. A compositionaccording to claim 1, which contains from 0.01 to 10% by weight of saidparticles.
 15. A composition according claim 1, which is in the formselected from the group consisting of an aerosol, roll-on, gel, stick,cream, lotion and pump spray formulation.
 16. An aerosol, roll-on, gel,stick, cream, lotion or pump spray device which includes a compositionaccording to claim
 1. 17. An aerosol, roll-on or gel, stick, cream,lotion or pump spray device which includes a composition according toclaim
 2. 18. A method of preventing or reducing malodour which comprisesapplying to the skin a deodorant composition as claimed in claim
 1. 19.A method of coating glass microspheres, which comprises heating anagitated mixture of glass microspheres, and a zinc compound in a liquidreaction medium, to form a milky suspension of colloidal zinc oxide, andfurther heating the suspension to 190° C. to 200° C. to deposit zincoxide as an adherent coating sintered on the glass microspheres.
 20. Amethod according to claim 19, wherein the mixture is heated to 140° C.to 160° C. to form said milky suspension.
 21. A method according toclaim 19, wherein the liquid reaction medium comprises a glycol.
 22. Amethod according to claim 21, wherein the glycol is selected from thegroup consisting of diethylene glycol and poly(ethylene glycol).
 23. Amethod according to claim 19, wherein the mixture is heated for 1 to 3hours to form said suspension, and for a further 1 to 3 hours to depositsaid coating.
 24. A method according to claim 20, wherein the mixture isheated for 1 to 3 hours to form said suspension, and for a further 1 to3 hours to deposit said coating.
 25. A method according to claim 19,wherein the zinc oxide coating is contacted with an acid to form thereona zinc salt.
 26. A method according to claim 25, wherein only part ofthe zinc oxide coating is converted to a zinc salt.
 27. A methodaccording to claim 25, wherein the acid is selected from the groupconsisting of a carboxylic acid and a phenol.
 28. A method according toclaim 27, wherein the carboxylic acid is selected from the groupconsisting of pidolic acid, acetic acid, euginol,pyrrolidone-S-carboxylic acid, cinnamic acid, citric acid and glycine.29. A method according to claim 25, wherein after forming the zinc salton the microspheres, they are washed with water without removal of thesalt.